In recent years, there is a tendency that the application of biometric authentication to the personal authentication in a portable terminal such as a smartphone or the like and the security authentication in a gate becomes widespread. Particularly, there have been many different attempts to apply fingerprint authentication to a portable terminal.
In general, when performing personal authentication through the use of a fingerprint, a false rejection rate may act as a factor sensitive to a user in the case of an electronic device having a high use frequency such as a portable terminal, e.g., a smartphone. Accordingly, it becomes a very important factor to reduce the false rejection rate by acquiring a larger amount of characteristic information on a user fingerprint.
However, a small fingerprint recognition sensor mounted to an electronic device such as a smartphone or the like has a relatively small size and, therefore, can acquire only an image which contains a partial region of the entire fingerprint. Thus, it is difficult for the small fingerprint recognition sensor to acquire a larger amount of characteristic fingerprint information.
For that reason, in an electronic device such as a portable terminal or the like provided with a small fingerprint recognition sensor, a plurality of fingerprint images is acquired in a fingerprint recognition process for registering an authentication-purpose fingerprint. For example, a portable terminal such as a smartphone or the like is designed so as to acquire several tens of registration-purpose fingerprint images.
In this connection, the number of registered fingerprint images is not necessarily proportional to the amount of fingerprint information. This is because fingerprint images may be continuously acquired in similar positions when acquiring a user's fingerprint.
In view of the aforementioned points, it is very important to guide a user to input a fingerprint in different positions. Most of conventional fingerprint recognition devices are configured to merely show a progress level of fingerprint registration through a progress bar or a change in image color.
Accordingly, the conventional method has a problem in that it is difficult to guide a user to acquire a fingerprint of a finger region other than a finger region whose fingerprint has been already acquired. This problem may eventually act as a major cause of increasing a false rejection rate at a fingerprint recognition (fingerprint authentication) step which will be performed after registration of a fingerprint (see, e.g., Korean Patent Application Publication No. 2010-0127432).